It is known that the handling of a motorcycle becomes heavy at low speeds if the steering column is too much inclined to the vertical (i.e., too nearly horizontal), whereas if the steering column is more nearly vertical the motorcycle handles well in low speed riding but handles poorly in fast riding because torques develop at high speeds that must be resisted or overcome by the driver.
U.S. Pat. No. 3,866,946 discloses an arrangement whereby a motorcycle can be adapted for desired speed conditions with the use of interchangeable parts, so that it is suitable either for slow riding, or for moto-cross riding or the like, or is especially adapted for fast riding such as occurs in motorcycle racing. To convert the motorcycle from suitability for one type of riding to another it must be partially disassembled. Therefore this arrangement has the disadvantage of being an either/or solution or a compromise solution which does not offer the possibility of adapting the motorcycle immediately to existing conditions, preferably even while it is being operated.
British Pat. No. 570,439 discloses a motorcycle with a steering column that is adjustable as to its angle of inclination, wherein the front fork is spaced to the front of a steering stem which is rotatable in the frame. The front fork is connected with that stem by means of upper and lower bracket plates which extend forward from upper and lower end portions of the stem. The fork has a pivotal connection to the lower bracket plate, and the upper bracket plate is confined to limited forward and rearward adjusting motion relative to the stem, having a forwardly and rearwardly elongated slot through which the upper end portion of the stem extends. The upper end portion of the stem is threaded, and nuts on it clampingly engage the upper bracket plate to hold the fork in any desired position of tilting adjustment relative to the axis of the stem. With this arrangement adjustment of the angle of inclination of the front fork could be accomplished only with the motorcycle at a standstill and with the aid of tools. This solution never found acceptance in practice because it did not allow the motorcycle to be adapted to a change in terrain or to changed riding conditions while it was being driven.